drm/shmobile: use drm_modeset_lock_all

Only a resume method to account for.

v2: Fixup compilation.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/shmobile/shmob_drm_drv.c b/drivers/gpu/drm/shmobile/shmob_drm_drv.c
index d1d5306..f6e0b53 100644
--- a/drivers/gpu/drm/shmobile/shmob_drm_drv.c
+++ b/drivers/gpu/drm/shmobile/shmob_drm_drv.c
@@ -313,9 +313,9 @@
 {
 	struct shmob_drm_device *sdev = dev_get_drvdata(dev);
 
-	mutex_lock(&sdev->ddev->mode_config.mutex);
+	drm_modeset_lock_all(sdev->ddev);
 	shmob_drm_crtc_resume(&sdev->crtc);
-	mutex_unlock(&sdev->ddev->mode_config.mutex);
+	drm_modeset_unlock_all(sdev->ddev);
 
 	drm_kms_helper_poll_enable(sdev->ddev);
 	return 0;